Old Time Baseball took the Tony La Russa Baseball engine (then the top baseball game in the market), removed the current 28 teams' players and ballparks, and substituted the complete lineups of every major league team from 1871 to 1981, 12,000 players in all. 16 old (often demolished) ballparks were also included in which games could be played with accurate dimensions.

The most remarkable feature in the game was the patented Baseball Time Machine, which allowed users to play any game in any individual year from 1871 through the present. This allowed users to play games in unique times like 1930, when baseball sought to lure fans during the Depression and juiced the ball so much that the batting average for baseball overall surpassed .300. The following year the ball was returned to more typical physics.

Other popular "let's see what happens" years for players were 1871, when the game visually looked more like softball, and 1942–45, when World War II stripped the major leagues of most of its established players.

The Baseball Time Machine allowed players to try to resolve the most famous baseball arguments of all time, What would happen if Sandy Koufax pitched to Babe Ruth?, How would the 1927 Yankees do against the Big Red Machine?, etc.

Daglow had written the basic mathematical models for the Baseball Time Machine in an unpublished 1980 game with the working title Apple Baseball, an extension of his Baseball game which he wrote on the then-new Apple IIpersonal computer before joining the Intellivision game design team. The diversion to Mattel delayed the introduction of the Baseball Time Machine by 15 years.

To create broad patterns of play that were easier to learn and less subject to extremes, the game also offered the chance to play games in any of six different major baseball eras:

1871–1892 -- Early Baseball, when the field dimensions were different and pitchers threw the ball softball-style, underhanded.

1893–1919 -- The Dead Ball Era, when the pitcher's mound location and pitching style matched modern baseball, but the ball was marginally softer and would not fly as far. During this era it was routine for 10 home runs to be the league leader's total, and a majority of those might be inside the parkhome runs that were the result of speed, not power.

1920–1945 -- The Babe Ruth Era, when then-pitcher Ruth changed the game by his tremendous power, and the live ball replaced the dead ball as baseball sought to make fans forget the Black Sox Scandal.

1961–1976 -- The Expansion Era, when baseball added many new teams, both increasing its influence and diluting its talent even as other sports like American football, basketball and ice hockey eroded its dominance of TV sports.

1977–1995 -- Modern Baseball, when continued expansion and the Free Agency created by the growth of the players union continued to change the game.

The game was a cult hit among serious baseball fans such as members of SABR and fans of sabermetrics, but entered the market during the baseball strike of 1994–1995 when many fans were angry at baseball in general. It never achieved mainstream success, and was sometimes criticized as being designed to please only hard-core baseball history "nuts". Since it was never updated or re-issued the game is one of the most expensive collectible PC games on eBay, since serious baseball fans will often bid up the price on good condition copies.